1. Field of the Invention
The present invention relates to an oil seal which is one kind of a sealing device. The oil seal according to the present invention is used, for example, as a shaft seal in a power steering section of a vehicle such as a motor vehicle or the like, or is employed in the other general industrial machines and the like.
2. Description of the Conventional Art
Historically, as an oil seal which has been used as the shaft seal in the power steering section of the vehicle such as the motor vehicle, an oil seal 51 shown in FIG. 3 has been known, and the oil seal 51 has a main lip 52 which is arranged toward an inner side A of the machine in an installed state and seals a sealed fluid such as an oil or the like, and a dust lip 53 which is arranged toward an outer side B of the machine and seals a foreign material such as a muddy water or the like (refer to Japanese Unexamined Patent Publication No. 2002-22028).
However, since a shaft is a vertical shaft in the case that the oil seal 51 is installed to an actual machine, the dust lip 53 is arranged in such a manner that a leading end of the lip is directed upward.
On the other hand, in a region in which a road improvement is not sufficient, for example, regions in foreign countries, a dust environment is severe and there is a case that the vehicle travels in a state in which the power steering section is temporarily submerged. In the case mentioned above, the muddy water is piled up in an upper part of the dust lip 53, in the oil seal 51. Accordingly, there is a problem that the muddy water entering from the dust lip 53 bites into the main lip 52 so as to cause an oil leakage.